On Thu, Mar 08, 2018 at 03:18:33PM +0200, Artem Bityutskiy wrote: > On Thu, 2018-03-08 at 18:53 +0800, Ming Lei wrote: > > Hi, > > > > This patchset tries to spread among online CPUs as far as possible, so > > that we can avoid to allocate too less irq vectors with online CPUs > > mapped. > > > > For example, in a 8cores system, 4 cpu cores(4~7) are offline/non present, > > on a device with 4 queues: > > > > 1) before this patchset > > irq 39, cpu list 0-2 > > irq 40, cpu list 3-4,6 > > irq 41, cpu list 5 > > irq 42, cpu list 7 > > > > 2) after this patchset > > irq 39, cpu list 0,4 > > irq 40, cpu list 1,6 > > irq 41, cpu list 2,5 > > irq 42, cpu list 3,7 > > > > Without this patchset, only two vectors(39, 40) can be active, but there > > can be 4 active irq vectors after applying this patchset. > > Tested-by: Artem Bityutskiy <artem.bityutskiy@xxxxxxxxx> > Link: https://lkml.kernel.org/r/1519311270.2535.53.camel@xxxxxxxxx Hi Artem, Thanks for your test! > > Ming, > > this patchset fixes the v4.16-rcX regression that I reported few weeks > ago. I applied it and verified that Dell R640 server that I mentioned > in the bug report boots up and the disk works. > > So this is not just an improvement, it also includes a bugfix. Actually, it isn't a real fix, the real one is in the following two: 0c20244d458e scsi: megaraid_sas: fix selection of reply queue ed6d043be8cd scsi: hpsa: fix selection of reply queue This patchset can't guarantee that all IRQ vectors are assigned by one online CPU, for example, in a quad-socket system, if only one processor is present, then some of vectors are still assigned by all offline CPUs, and it is a valid case, but still may cause io hang if drivers(hpsa, megaraid_sas) select reply queue in current way. Thanks, Ming
